Section
4 Information required
4.1 General
4.1.3 Plans are generally to be submitted in triplicate, but only one copy of
supporting documents and calculations will be required.
4.2 Plans and supporting information
4.2.1 Plans covering the following items are to be submitted for approval, as
relevant to the type of unit:
- Bilge keel details.
- Bracings and associated primary structure.
- Corrosion control scheme.
- Deck structures including pillars and girders.
- Double bottom construction.
- Engine room construction.
- Equipment and supports.
- Erection sequence.
- Footings, pads or mats.
- Fore and aft end construction.
- Helideck.
- Ice strengthening.
- Leg structures and spuds.
- Loading manuals, preliminary and final.
- Machinery seatings.
- Main hull or pontoon structure.
- Masts and derrick posts.
- Materials and grades.
- Midship sections showing longitudinal and transverse
material.
- Penetrations and attachments to primary structure.
- Profile and decks.
- Quality control and non-destructive testing procedures.
- Riser support structures.
- Rudder, stock, tiller and steering nozzles.
- Shell expansion.
- Stability columns.
- Stern frame and propeller brackets.
- Structural categories.
- Structural bulkheads and flats.
- Structure in way of jacking or elevating arrangements.
- Superstructures and deckhouses.
- Support structures for cranes, masts, derricks, flare towers
and heavy equipment.
- Tank boundaries and overflows.
- Tank testing procedures and schedules.
- Temporary anchoring equipment.
- Towing arrangements and equipment.
- Transverse and longitudinal sections showing scantlings.
- Watertight sub-division.
- Watertight and oiltight bulkheads and flats.
- Watertight and weathertight doors and hatch covers.
- Welding details and procedures.
4.2.2 The following supporting plans and documents are to be submitted:
- General arrangements showing decks, profile and sections
indicating all major items of equipment and machinery.
- Calculation of equipment number.
- Capacity plan.
- Cross curves of stability.
- Cross curves of allowable V.C.G.
- Design deck loading plan.
- Dry-docking plan.
- Operations Manual, see
Pt 3, Ch 1, 3 Operations manual.
- Tank sounding tables.
- Wind heeling moment curves.
- Lines plan or equivalent.
- General arrangement showing moorings for tandem and side by side
offloading. This is to include the maximum and minimum dimensions and main
particulars for the range of shuttle tankers that are permitted to attend.
For each mooring line, the breaking load and the maximum and minimum angles
(horizontal and vertical) between the line and the offshore unit are to be
stated.
- General arrangement showing barge mooring arrangements
where barges are to be moored alongside the unit.
4.3 Calculations and data
4.3.1 The following calculations and information are to be submitted where
relevant to the unit type and its design:
- Proposed class notations, operating areas and modes of
operation, list of operating conditions stating proposed draughts.
- Design environmental criteria applicable to each mode,
including wind speed, wave height and period, or sea state/wave energy
spectra (as appropriate), water depth, tide and surge, current speed,
minimum air temperature, ice and snow loads, sea bed conditions.
- A summary of weights and centres of gravity of lightship
items.
- A summary of all items of deadweight, deck stores/ supplies,
fuel, fresh water, drill water, bulk and sack storage, crew and effects,
deck loads (actual, not design allowables), riser, guideline, mooring
tensions, hook or derrick loads and ballast schedules. The summary should be
given for each operating condition.
- Details of distributed and concentrated gravity and live design
loadings including crane overturning moments.
- Tank content data, and design pressure heads.
- Details of tank tests, model tests, etc.
- Strength and fatigue calculations.
- Calculation of hull girder still water bending moment and shear
force as applicable.
- Calculation of hull girder section modulus at midships and
elsewhere as required by LR. Additional calculations to verify longitudinal
strength may be required when:
- The maximum hogging and sagging combined still water and
vertical wave bending moments do not occur at midship.
- The structural arrangement at midship changes to a
different arrangement within the 0,4L midship region.
- Stability calculations for intact and damaged cases covering a
range of draughts to include all loading conditions.
- Documentation of damage cases, watertight subdivision and limits
for downflooding.
- Freeboard calculation.
4.4 Specifications
4.4.1 Adequate design specifications in appropriate detail are to be submitted
for information.
4.4.2 Specifications for the design and construction of the hull and structure
are to include materials, grades/standards, welding construction procedures and
fabrication tolerances.
4.4.3 Specifications related to the unit’s proposed operations are to include
environmental criteria, modes of operation and a schedule of all model tests with
reports on minimum air gap, motion predictions, mooring analysis, etc.
Specifications and reporting for wave basin, wind tunnel and ice tank model testing
are to be in accordance with 4.6.
4.5 Plans to be supplied to the unit
4.5.1 The following plans and documents are to be placed on board the unit,
see
Pt 3, Ch 1, 2 Information required:
- Operations Manual.
- Loading Manual.
- Construction Booklet.
- Main scantlings plans.
- Corrosion control system.
- Electrical cables schedule of watertight penetrations (e.g. cable transit
seal systems register).
4.5.2 Where an OIWS (In-water Survey) notation is to be assigned,
approved plans and information covering the items detailed in Pt 3, Ch 1, 2 Information required are also to be placed on board.
4.5.3 Where a ShipRight CM (Construction Monitoring) notation or
descriptive note is to be assigned, the approved Construction Monitoring Plan (CMP),
as detailed in the ShipRight Construction Monitoring Procedures, is to be
maintained on board the unit.
4.6 Model test specifications and
reporting
4.6.1 Model testing is to be carried out by a competent test facility which, at
the discretion of LR, may require witnessing by the Surveyor. Attendance by LR would
typically be limited to witnessing novel designs, novel testing techniques and at
test facilities that LR is unfamiliar with. The suitability of the proposed test
facility is to be discussed with LR at the earliest opportunity.
For test facilities that LR is unfamiliar with, a review of the internal
quality assurance procedures of the proposed test facility may be required. The
model test specification is to be submitted for review and is to be agreed with by
LR before the commencement of the model tests.
4.6.2 The model is to be of an adequate scale for its intended purpose and
fully representative of the features of the unit under consideration. Account is to
be taken of the different draughts, trim, deck structures, topside structures and
large equipment appendages as applicable (e.g. anchor racks or thrusters fairleads,
turret and turntable configuration, risers) and appropriate to the type and purpose
of the test.
4.6.3 Specifications for model tests are to include the following information
with respect to the model, and as appropriate to the unit type and its design:
- Particulars and hydrostatic parameters including displacement,
draught, trim, centres of buoyancy and gravity.
- Loading conditions and draughts to be tested and method of
ballasting or loading.
- Lines plan, body plan and general arrangement.
- Mooring systems and anchor points, including general
arrangement, groupings and positioning, angles, material properties and
details of any truncations or substitutions to be made to account for basin
limitations. For deep water moorings, the scale and any truncation technique
used in the model of the positional mooring system (and risers where their
damping contribution may be significant) will be subject to special
consideration. Procedures for static load-displacement tests and stiffness
simulation to ensure correct modelling of the mooring systems are also to be
specified.
- Station keeping model tests are to represent the positional
mooring system main characteristics as closely as practicable taking into
consideration:
- Mooring line components stiffness (linear or
non-linear);
- Mass and inertia properties;
- Drag and added mass; and
- Interaction with sea-bed.
- Chosen scaling method including the relationships between the
parameters to be used and any assumptions made as a result of scaling
limitations. In addition, comparisons between full scale and model Reynolds
and Froude numbers and drag coefficients are to be provided for the
applicable environmental conditions.
- A description of the sign convention to be used.
- A list of tolerances to be used for the model testing pertaining
to the model, facility and simulated environmental conditions. Modelling
tolerances are to be in accordance with ITTC Recommended Procedures.
- Required materials and properties, types and colours of coatings
to be used and details of all markings and lines to be applied. All
components of the model must be coated in a colour to ensure high visibility
on photographs and video and markings are to include section lines and draft
marks at forward, aft and midship. Positions of any turbulence stimulators
must also be clearly marked.
- A summary of the construction of all components of the model,
including equipment, working and finishing methods to be used.
- For ship units fitted with an internal turret, the model
specification for the turret is to include the general arrangement, turret
dimensions and the method for assessing trapped water loads and motions
inside the moonpool.
- For tension-leg units, the model specification for the tendon
system is to include a detailed description of the required physical and
force characteristics and material properties of the tendons.
- For units fitted with risers, the properties of the risers in
the model test are to be specified including their position, configuration,
masses, drag coefficients and axial and bending stiffness. A description of
all riser configurations to be tested is also to be included.
- Topside configuration including general arrangement. For wave
basin testing, where parts of the topsides are submerged in accidental
conditions and/or extreme sea states, the modelled topsides must be of
sufficient detail to provide correctly reproduced hydrostatics for the
model.
- Where wind tunnel testing is to be performed, an
above-waterline model of the unit at loaded and ballast draughts is to be
used, constructed to a suitable scale to avoid a blockage ratio of greater
than five per cent. Topsides are to be modelled in as much detail as
practicable by manufacturing limits to accurately simulate the wind profile
over the topsides of the full scale.
- For units fitted with thrusters, the specification for
modelling the thrusters is to include the required thrust force and heading
control. Any simplification of the thruster system is to be in such a way as
to not affect the required forces and moments on the unit.
4.6.4 Specifications are also to include the following information relating to
the test procedures, as appropriate to the unit type and extent of required
testing:
- Specifications of the appropriate signals and response data to
be recorded during the tests, including recording methods and positions of
any relevant instrumentation on the model. The data is to be sufficient so
that a conclusive comparison between the model tests and the corresponding
simulation results can be performed. The sample rate is to be at least ten
times the highest response frequency that needs to be observed. An
appropriate anti-aliasing filter should be used.
- Specifications for calibration of the following items as
applicable to the unit:
- All necessary instrumentation, sensors and equipment.
Accuracies must be verified in accordance with manufacturers’
guidelines.
- Model particulars, including dimensions, masses and
load distributions.
- Restoring forces from mooring lines and risers.
- Natural periods of the unit.
- Simulated environmental conditions.
- Motion and acceleration tests of the unit are to be in six
degrees of freedom about the centre of gravity in both regular and irregular
wave conditions and are to include details of the chosen axis reference
points on the model and methods for deriving motions at the centre of
gravity from the recorded data. The same reference points are to be used for
the model tests and post-processing of the results to facilitate comparison.
Where it is not possible to measure directly at the centre of gravity e.g.
when the centre of gravity lies outside the physical volume of the unit, the
method to determine the motions and accelerations at the centre of gravity
is to be documented.
Turret forces, mooring line and riser
tensions are also to be recorded where fitted.
- Wave basin tests are to be of sufficient duration to establish
the low frequency behaviour and most probable maxima with sufficient
reliability whilst providing also sufficient time to allow start up
transient phenomena (associated with either the floating unit or the wave
basin) to die down to acceptable levels.
- Wave basin station keeping model tests records are to focus on
establishing the main characteristics of responses (e.g. mooring line
tensions, offset of the offshore unit and turret loads when applicable) such
as:
- Mean of response;
- Standard deviation and distribution of peak values of
wave frequency response; and
- Standard deviation and distribution of peak values of
low frequency response.
Most probable maximum values of response should also be
estimated
- For tests where force sensors are under continuous tension
(e.g. mooring tests) and that tension is of importance to model response
(e.g. pre-tension in mooring lines influences natural periods) this
pre-tension level should be measured and documented at regular intervals
throughout the test campaign. As a minimum this should be done once a
day.
- Where air gap testing is required, the specification is to
include details of the location of air gap measuring points and the range of
wave heights to be tested. This is to be representative of the expected site
conditions. A typical number of measuring points for air gap tests for a
semi-submersible is nine, spaced evenly across the model.
- Water elevation testing for internal turrets is to include
measurements at a sufficient number of locations to determine the variation
in water elevation profile, typically at a minimum of three different
locations. Relative wave elevations are also to be provided external to the
unit on both the port and starboard sides adjacent to the turret axis.
- Evidence that the effects of wave reflection and critical
resonance of the natural frequencies of the wave basin and the modelled
mooring system have been considered and mitigated for.
- Wave heights during wave generation are to be measured
separately at the intended location of the unit before the test in order to
provide correct reference heights for the motion test analysis. Wind and
current speeds should also be measured during calibration of environments
before the test.
- Inclination tests to verify values of metacentric height, GM
(roll for mono hulls and roll and pitch for column-stabilised units) are to
be carried out at the start of the model test programme. Each inclination
test is to include at least three data points, preferably five, with the
assessment of GM-value to be done by regression on these data points.
- Decay tests are to be performed for all degrees of motion and
for the loading conditions specified in Pt 4, Ch 1, 4.6 Model test specifications and reporting 4.6.3. The amplitudes tested for damping are to be
representative of the expected motions for the on-site conditions. The
expected results are to include relative critical damping percentages and
natural periods for all amplitudes tested in addition to mooring line and
riser tensions, where fitted.
- Where towing tests are to be carried out, they are to include
measurement of the motions and accelerations of the unit in six degrees of
freedom about the centre of gravity (see also
Pt 4, Ch 1, 4.6 Model test specifications and reporting 4.6.5(c)) and relative wave elevations at a
sufficient number of locations to determine the variation in water elevation
profile, typically at a minimum of nine locations along the hull and three
locations around the turret or moonpool, if fitted. Wave pressures are to be
taken by means of sensors at typically eight locations on the model hull.
Towing speeds, accelerations and line tensions are also to be recorded.
- Tests of green water occurrence, wave run-up and slamming are
to be performed at sufficient sampling intervals such that peak loadings are
captured. Load gauges to measure green water impact pressures are to be
mounted at various locations on the model (e.g. bow area, accommodation,
exposed decks or horizontal braces and exposed equipment). The locations are
to be agreed with LR depending on the specific design. Typically at least
eight load gauges to measure green water impact pressures are to be
distributed evenly over the length and breadth of the hull. Typically at
least eight sensors to measure the impact pressures are to be positioned on
the bow, forward deck and stern of ship units.
- Where bathymetry is to be modelled, schematics of the surveyed
sea bed contours are to be provided in the specification, in addition to a
description of the bathymetry as modelled.
- Where ice basin tests are to be carried out, details of the
modelled ice properties for each test are to be provided, including the
types of ice (e.g. ridge, brash and floe), concentration and size
distribution of ice pieces, thicknesses, densities and flexural strengths.
The method of ice production is also to be specified. Ice basin tests are to
be taken for several drift angles and velocities. Motions and accelerations
of the unit in ice are to be recorded in six degrees of freedom about the
centre of gravity, (see also
Pt 4, Ch 1, 4.6 Model test specifications and reporting 4.6.5(c)). Ice-induced pressures on the unit are to
be recorded using a sufficient number of sensors positioned at the bow,
midship and aft to accurately record the distribution of ice pressures over
the hull. A typical number for a ship unit would be eight sensors.
Ice-induced forces and moments are to be measured using an appropriate load
cell arrangement. Unless it can be demonstrated that there is no
interference between the measurement of ice-induced pressures and
ice-induced forces and moments, these are to be measured in tests
independent of each other.
- Wind tunnel tests are to be carried out using a model built to
the specification provided in Pt 4, Ch 1, 4.6 Model test specifications and reporting 4.6.3. The wind tunnel is to be set up using
appropriate equipment to correctly simulate the required wind profile and
boundary layer as appropriate to the on-site conditions. Wind forces and
moments are to be measured for 0-360 degrees in increments no greater than
10 degrees.
- A schedule of all tests to be performed and details of the
corresponding results and deliverables are to be provided as part of the
specification.
4.6.5 The model test reports are to demonstrate that the specification has
been complied with, through submission of the following information:
- A report documenting the procedures that have been followed for
both set-up and carrying out the tests.
- A summary of the model manufacture and set-up, including
as-built drawings, materials and construction methods.
- Calibration test reports and results.
- Test results corresponding to the specification schedule.
- Commentary on the test results, including any comparisons with
numerical simulation results. Any comparisons are to be accompanied by the
corresponding numerical data.
- Colour photographic evidence supporting the report including the
following:
- Construction of all manufactured components involved in
the model testing.
- Instrumentation and measurement device positions on the
model.
- Basin set-up, bathymetry and positions of tank
instrumentation.
- Environmental set-ups without model, e.g. wave
generation.
- Calibration test set-up.
- Set-up for each test.
- Video recordings of all tests performed, clearly showing
environmental conditions and model performance, to be accompanied by video
stills taken at appropriate intervals throughout the test. A video log
describing the date, time and identification of the test shown is also to be
provided.
- A chronologic test log describing for each test:
- Date.
- Time.
- Test set-up.
- Environmental conditions.
- Model heading.
- Remarks / observations.
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